A simple blanch‐dry process for lipoxygenase inactivation in soybean cotyledons

Abstract

SummaryFull‐fat flour from unblanched soybeans develops a beany flavour during milling due to lipoxygenase activity; the flour also becomes bitter during storage. The minimum thermal treatment necessary to inactivate lipoxygenase in soybeans before milling was determined. Soybeans were dehulled and cotyledons blanched in water between 80 and 99.3°C. Water blanching for 3 min at 99.3°C was necessary when blanched cotyledons were subsequently sun dried, and the flour had a nitrogen solubility index (NSI) of 37.8% and residual trypsin inhibitor activity (TIA) of 64.2%. Only 1.5 min blanching was necessary to inactivate lipoxygenase in soy cotyledons if they were dried subsequently at 60°C; NSI of this flour was 32.7%, with 44.7% residual TIA.